1. Field of the Invention
The present invention relates to a light guide for illuminating keys of a keyboard and/or a keypad, and also relates to a process for making the light guide.
2. Discussion of the Related Art
Portable electronic devices usually include keyboards and/or keypads for inputting information. When portable electronic devices are used in the dark, the keys need to be illuminated. Light guides are used to transfer light rays from a light source to illuminate the keyboards and/or the keypads of the portable electronic devices. In a typical portable electronic device such as a mobile phone, the light guide is positioned between a printed circuit board and the display and/or keyboard. The light guide can for example be a light emitting diode (LED). The light guide conveys the light rays from the LED, to illuminate the display and/or keyboard.
Referring to FIG. 6, a typical keypad light guide 10 for a mobile phone is shown. The light guide 10 includes a transparent base sheet 11, a light entrance 12 located at one side of the base sheet 11, and a regular array of apertures 13 defined on the base sheet 11. The apertures 13 correspond to shapes of keys (not shown). Each aperture 13 is surround by an up-standing collar 14 integrally formed with the base sheet 11. Light rays are introduced into the light guide 10 from a distributed light source (not shown) such as an LED disposed adjacent to the light entrance 12. The collars 14 have chamfered side faces. The side surfaces are roughened meaning that they are optical imperfect and causes light rays to escape. Thus, the light guide provides an illuminated ring around the key. However, the structure of the light guide 10 is complex.
Typically, the light guide 10 is manufactured by injection molding technology. With a requirement for a thin type light guide, an injection mold for making the thin light guide is required to have great pressing capability. This means the injection mold may be a complex apparatus. Such injection mold is expensive and may require much maintenance, thus increasing the cost of injection molding. In addition, in industry, in order to mass-produce the light guides, the injection molds usually have a plurality of cavities for making a plurality of light guides at a same process. However, in a same pressing process, the light guides may have differing pressures applied by the injection mold, such that the light guides have non-uniform thickness.
What is needed, therefore, is a new process for making a light guide which can overcome the above-described shortcomings. What is also needed is an efficacious light guide made according to such process.